a. Field of the Invention
The instant invention is directed toward a transition apparatus for use with a medical device having an elongate element, including an apparatus that is configured to use the elongate element itself for attachment of at least a portion of the transition apparatus to the medical device.
b. Background Art
In a normal heart, contraction and relaxation of the heart muscle (myocardium) takes place in an organized fashion as electrochemical signals pass sequentially through the myocardium from the sinoatrial (SA) node located in the right atrium to the atrialventricular (AV) node and then along a well defined route which includes the His-Purkinje system into the left and right ventricles. Atrial fibrillation results from disorganized electrical activity in the heart muscle, or myocardium. An increasingly common medical procedure for the treatment of certain types of cardiac arrhythmia and atrial arrhythmia involves the ablation of tissue in the heart to cut off the path for stray or improper electrical signals.
Ablation may be performed either from within the chambers of the heart (endocardial ablation) using endovascular devices (e.g., catheters) introduced through arteries or veins, or from outside the heart (epicardial ablation) using devices introduced into the chest. The ablation devices are used to create elongated transmural lesions—that is, lesions extending through a sufficient thickness of the myocardium to block electrical conduction—which form the boundaries of the conductive corridors in the atrial myocardium. The ablation devices create lesions at particular points in the cardiac tissue by physical contact of the cardiac tissue with an ablation element and the application of energy.
One difficulty in obtaining an adequate ablation lesion is the dynamic movement of the heart, especially when there is an erratic or irregular heart beat. Another difficulty in obtaining an adequate ablation lesion is maintaining sufficiently uniform contact with the cardiac tissue across the length of the ablation element surface. Without sufficiently continuous and uniform contact, the associated ablation lesions may not be adequate.
An epicardial ablation device may be used to create uniform, continuous, linear lesions during cardiac ablation. The device may be positioned securely around a patient's atrium while the ablation elements of the device apply energy (e.g., high intensity focused ultrasound energy) to the targeted tissue. Each ablation element is retained by a cell carrier. Cell carriers located at the distal and proximal end of the device are configured to provide for attachment of at least one elongate element (e.g., leash). The elongate elements may be configured to be tensioned together to generally connect the ends of the device together so that the device may encircle the cardiac tissue to be ablated.
An introducer may be used to position the ablation device. For example, the introducer may be advanced around the pulmonary veins, and the distal end of the ablation device may then be attached to the proximal end of the introducer. The introducer may be pulled further to wrap the ablation device around the pulmonary veins. In a conventional epicardial ablation device, a blunt transition piece (e.g., releasable assembly) made of rigid plastic is connected to the distal end of the ablation device for connection to the proximal end of the introducer. The blunt transition piece may produce drag during introduction of the device into the patient. Furthermore, in conventional epicardial ablation devices, the transition piece may be attached to the device with sutures, requiring the operator of the device (e.g., a surgeon) to cut at least one of the sutures to free the transition piece (with attached introducer) from the device. Finally, the rigid transition piece provides no management of the elongate elements (e.g., leashes), which increases drag during device introduction and may make it difficult for the operator to locate the elongate elements once the device is ready for final placement around the cardiac tissue. Accordingly, many operators of the medical device tie a suture to attach the elongate elements to the introducer to bring the elongate elements at least partially out of the body to ease the step of locating the elongate elements. Operators then have to later remove that added suture to free the elongate elements.
Thus, there remains a need for a transition apparatus for use with a medical device having an elongate element that is configured for ease of connection to the introducer and detachment from the medical device, without increasing drag during medical device introduction and without time-consuming suturing operations to connect the transition apparatus to the medical device.